skip to content
A brown mussel with orangish brown striations
Information icon An orangefoot pimpleback mussel. Photo by Monte McGregor, Center Mollusk Conservation, Kentucky DFWR.

Orangefoot pimpleback

Plethobasus cooperianus

  • Taxon: Bivalve
  • Range: Alabama, Illinois, Kentucky and Tennessee
  • Status: Endangered. Some populations in the French Broad and Holston Rivers are experimental.


The orangefoot pimpleback is a medium size mussel, 3 to 4 inches in length. The shell is thick and circular in outline. The surface of the shell has dark concentric growth rings and the posterior two-thirds of the shell is covered with raised tubercles. Number, size, and shape of the tubercles is variable. The color of the shell is yellowish brown to chestnut brown in color, and it darkens as individuals become older. Light greenish rays are found only in younger individuals. Nacre color varies from white to pink.


This mussel species inhabits medium to large rivers.


Mussels are filter feeders; they mainly eat phytoplankton, zooplankton, and bacteria suspended in the water. By drawing water inside their shells through a siphon, their gills filter out food and take in oxygen.

Historical range

It historically occurred in the Ohio, Cumberland, and Tennessee River systems, including the lower French Broad and Holston Rivers.

Current range

The species persists in the lower Ohio, Tennessee, and Cumberland Rivers.

Counties where the species is present or believed to occur

  • Alabama: Colbert and Lauderdale counties
  • Illinois: Massac and Pulaski counties
  • Kentucky: Ballard, Livingston, Marshall, and McCracken counties
  • Tennessee: Anderson, Bedford, Benton, Bledsoe, Blount, Campbell, Cheatman, Claiborne, Davidson, Decatur, Dickson, Giles, Hamilton, Hancock, Hardin, Henderson, Hickman, Houston, Humphreys, Jefferson, Knox, Lewis, Loudon, Macon, Marion, Marshall, Maury, McMinn, McNairy, Meigs, Monroe, Perry, Rhea, Roane Robertson, Rutherford, Sequatchie, Sevier, Smith, Stewart, Sumner, Trousdale, Union, Wayne, Williamson, and Wilson counties

Conservation challenges

The primary threat to this species is impoundment of rivers for flood control, navigation, and hydroelectric power generation. Siltation and pollution of rivers have also contributed to the decline of the orangefoot pimpleback.

How you can help

  • Individuals can do a number of things to help protect mussels, such as:
  • Conserving water to allow more water to remain in streams.
  • Using pesticides responsibly, especially around streams and lakes, to prevent runoff into mussel habitats.
  • Controlling soil erosion by planting trees and plants to avoid runoff of sediments into freshwater areas.
  • Supporting practices for construction and maintenance of unpaved, rural dirt and gravel roads that minimize erosion and connectivity to our rivers and lakes.
  • Supporting and follow zebra mussel quarantine, inspection, and decontamination programs to prevent the spread of zebra mussels, an invasive species that competes with native mussels.

Subject matter experts

Designated critical habitat

No critical habitat is designated for this species.

Additional resources

Federal Register notices

The following Federal Register documents were automatically gathered by searching the Federal Register Official API with this species’ scientific name ordered by relevance. You can conduct your own search on the Federal Register website.

  • We're sorry but an error occurred. Visit the Federal Register to conduct your own search.

Contact Us:

Looking for a media contact? Reach out to a regional spokesperson.

Share this page

Tweet this page on Twitter or follow @USFWSsoutheast

Share this page on Facebook or follow USFWSsoutheast.


Share this page on LinkedIn